General Description

The general responsiility of our group is to provide a Recovery Manager for MINIREL. It is based on the ARIES recovery algorithms. We provide methods with which a transaction may abort and take care of the system after a crash. The Recovery Manager also provides methods to write log records during the normal operating mode.


The Recovery Manager has a "Rollback" method with which transactions are aborted. When a transaction aborts, all references of the transaction are removed from the data pages and an abort log record and CLRs are written to the appropriate log file.

During normal operation, the Recovery Manager provides methods to log update and commit operations to the log file. That is, the manager takes care of the format of the update and commit log records.

The real work of the Recovery Manager is after a crash. The "Restart" rooutines take care of the three phases : Analysis, Redo and Undo, and restore the system to a consistent state.

The Recovery Manager also takes care of checkpointing. During checkpointing the dirty page table and transaction tables are written to the log file. After a crash, the analysis phase starts from the log record of the last checkpoint.

Interaction with other groups

• The Recovery Manager uses the Log Manager interface to write and read log records from the log file. We, however determine the format of the log records to be written to the log file.
• We interact with the Buffer Manager in order to acquire the Dirty Page Table, which is logged during a checkpoint.
• The OS group provides us with a method to acquire the Transaction table. This is again, logged during a checkpoint. We also update the LastLSN field of the Transaction table.
• Finally, we interact with the lock manager. During the restart mode of operation, the entire database needs to be locked and the locking methods are used.